Monitoring of microsurgically and endovascularly treated aneurysms (META): protocol for an international multicentre retrospective cohort study.

Introduction: Following endovascular treatment (EVT) or microsurgical treatment (MT) of intracranial aneurysms (IA), radiological follow-up is performed to assess for recurrence and to determine the need for re-treatment. There is a paucity of evidence describing the long-term results of EVT and MT for IA and therefore data to inform the design of follow-up protocols are lacking. The overarching aim of the META study is to determine the clinically relevant long-term outcomes of EVT and MT for IA, and use this data to create evidence based radiological and clinical follow-up protocols for these aneurysms.

Methods And Analysis: The META study will be a multicentre, retrospective cohort study. Data collection will begin in June 2024 and all IA treated with EVT or MT meeting inclusion criteria between 1st January 2013 and 31st of December 2013 will be included, to allow for a maximum of 10 years of radiological and clinical follow-up. Clinical and radiological data will be collected and stored on a secure online database. Following the completion of data collection, factors associated with re-treatment or subarachnoid haemorrhage from an aneurysm treated with EVT or MT will be identified and used to risk stratify IAs, with a view to developing an evidence-based follow-up protocol of IA treated with EVT or MT.

Ethics And Dissemination: This project will be registered with the Royal College of Surgeons in Ireland (RCSI) Research Ethics Committee (REC). It will also be registered locally at each participating centre and appropriate local approvals will be obtained. The results of the study will be disseminated through presentation at national and international meetings, and publication in peer reviewed journals.

Strengths And Limitations: This study will be the first contemporary multicentre study examining the long-term outcomes following treatment of ruptured and unruptured intracranial aneurysms.Our study will follow up treated aneurysms over a prolonged period of up to ten years; such prolonged follow-up is essential in the counselling of patients with this pathology, the majority of whom are in the fifth and sixth decades of life.The multicentre study design will increase the external validity and applicability of the results.The study will not assess aneurysm occlusion directly; data on significant aneurysm recurrences requiring re-intervention or leading to aneurysm rupture will be collected.

Plain English Summary: Intracranial aneurysms (IAs) are abnormal outpouchings or dilations on the main blood vessels supplying the brain. 3% of the general population have IAs and the majority will remain asymptomatic however a proportion will go on to rupture and cause subarachnoid haemorrhage (SAH), which is a condition associated with a significant rate of death and disability. The treatment of both ruptured and unruptured IAs aims to prevent future aneurysm rupture leading to SAH. Historically, the only treatment modality for IAs was a neurosurgical operation called microsurgical clipping but more recently endovascular treatment, whereby the aneurysms can be treated using catheters inserted into the arteries of the groyne or wrist has become the predominant treatment. However, there are very few studies describing the long-term outcomes of microsurgical clipping or endovascular treatment, particularly with respect to the requirement for aneurysm re-treatment or SAH due to rupture of a previously treated aneurysm. The aim of this study is to assess the outcomes following microsurgical clipping and endovascular treatment of a large number of both ruptured and unruptured IA over an extended follow-up period, with a view to providing data that will permit us to optimise the follow-up of patients with IA following treatment.